Breaking down the barriers to cancer immunotherapy

Spontaneous Remission of Acute Lymphoblastic Leukemia Following Candida tropicalis Fungemia

Spontaneous remission (SR) in acute lymphoblastic leukemia (ALL) is a poorly understood phenomenon that has been sporadically reported in medical literature for over a century, and the molecular and immunologic mechanisms of remission pose interesting clinical questions. Furthermore, the often-transient nature of these remissions poses a challenge to physicians in formulating an approach to treatment. We report on a rare case of Candida tropicalis sepsis in a three-year-old female with high-risk ALL who received less than two months of treatment prior to sepsis and subsequent SR.

Recent advances in overcoming barriers to cell-based delivery systems for cancer immunotherapy

Immunotherapy strategies that use cell-based delivery systems have sparked much interest in the treatment of malignancies, owing to their high biocompatibility, excellent tumor targeting capability, and unique biofunctionalities in the tumor growth process. A variety of design principles for cell-based immunotherapy, including cell surface decoration, cell membrane coating, cell encapsulation, genetically engineered cell, and cell-derived exosomes, give cancer immunotherapy great potential to improve therapeutic efficacy and reduce adverse effects. However, the treatment efficacy of cell-based delivery methods for immunotherapy is still limited, and practical uses are hampered due to complex physiological and immunological obstacles, such as physical barriers to immune infiltration, immunosuppressive tumor microenvironment, upregulation of immunosuppressive pathways, and metabolic restriction. In this review, we present an overview of the design principles of cell-based delivery systems in cancer immunotherapy to maximize the therapeutic impact, along with anatomical, metabolic, and immunological impediments in using cell-based immunotherapy to treat cancer. Following that, a summary of novel delivery strategies that have been created to overcome these obstacles to cell-based immunotherapeutic delivery systems is provided. Also, the obstacles and prospects of next-step development of cell-based delivery systems for cancer immunotherapy are concluded in the end.

Engineered Attenuated Salmonella typhimurium Expressing Neoantigen Has Anticancer Effects

Neoantigen vaccines are an immunotherapy strategy for treating cancer. The vaccine degrades quickly, so the strategy must include protection and precise targeting for immune cell stimulation. In this study, we engineered attenuated Salmonella typhimurium, which is highly infiltrative to tumors, to act as a carrier for Neoantigen peptide vaccine. Our system used a constitutive promoter vector, so that a single injection of Salmonella expressing Neoantigen could be used without requiring additional induction injections. In vivo experiments on bacteria-treated mice showed that Neoantigen expressed by the engineered carrier infiltrated tumors and resulted in suppressed tumor growth, higher survival rates and longer survival times, a relative increase of CD4 and CD8 T cells, and cytokine release. These results indicate that engineered Salmonella can be used as a carrier for Neoantigen immunotherapy.

Spontaneous remission of acute lymphoblastic leukemia: A case report

Spontaneous remission (SR) in acute lymphoblastic leukemia (ALL) is a rare phenomenon, but the disease course and its underlying processes are of basic and clinical interest. Herein is reported the case of a pregnant, 31-year-old patient who developed ALL, followed by septic shock and SR of ALL. Information is summarized from earlier case reports and incidences of SR in ALL, to identify common patterns. Furthermore, the phenomenon of SR is compared with another disease variant of ALL, termed prodromal or preceding-ALL (pre-ALL). SR and the aleukemic phase in pre-ALL are associated with fever and/or sepsis and have similar kinetics and epidemiology. Therefore, pre-ALL not only closely resembles SR in ALL, but both conditions may represent a single disease entity. Production of pro-inflammatory cytokines and immune cell effects may induce temporary remission of ALL and the suppression of hematopoiesis. In contrast to SR in other types of cancer, all documented cases of SR in ALL were only transient. However, the disease can still be effectively treated with standard ALL therapies following relapse.

Toll-like receptor-5 agonist, entolimod, suppresses metastasis and induces immunity by stimulating an NK-dendritic-CD8+ T-cell axis

Activation of an anticancer innate immune response is highly desirable because of its inherent ability to generate an adaptive antitumor T-cell response. However, insufficient safety of innate immune modulators limits clinical use to topical applications. Toll-like receptor 5 (TLR5) agonists are favorably positioned as potential systemic immunotherapeutic agents because of unusual tissue specificity of expression, uniquely safe profile of induced cytokines, and antitumor efficacy demonstrated in a number of animal models. Here, we decipher the molecular and cellular events underlying the metastasis suppressive activity of entolimod, a clinical stage TLR5 agonist that activates NF-κB-, AP-1-, and STAT3-driven immunomodulatory signaling pathways specifically within the liver. Used as a single agent in murine colon and mammary metastatic cancer models, entolimod rapidly induces CXCL9 and -10 that support homing of blood-borne CXCR3-expressing NK cells to the liver predominantly through an IFN-γ signaling independent mechanism. NK cell-dependent activation of dendritic cells is followed by stimulation of a CD8(+) T-cell response, which exert both antimetastatic effect of entolimod and establishment of tumor-specific and durable immune memory. These results define systemically administered TLR5 agonists as organ-specific immunoadjuvants, enabling efficient antitumor vaccination that does not depend on identification of tumor-specific antigens.

Genetic variations in cytotoxic T-lymphocyte antigen-4 and susceptibility to cervical cancer

Cytotoxic T-lymphocyte antigen-4 (CTLA-4), a molecule expressed predominantly on activated T cells, plays an important role in the down-regulation of T-cell activation. To evaluate the potential effects of CTLA-4 gene polymorphisms on susceptibility to cervical cancer, we genotyped polymorphisms in CTLA-4 (- 318 T/C, CT60 G/A,+49 G/A, - 658 T/C, and - 1661 G/A) and calculated odds ratios for the genotype and allele distributions between patients and controls. We then examined the functional relevance of the polymorphisms using enzyme-linked immunosorbent assays (ELISAs), in vitro lymphocyte proliferation assay, and cytotoxic assay. The CTLA-4 - 318 CC, CT60 AA, and+49 GG genotype frequencies were lower in patients than in controls (p <0.05). The frequencies of CTLA-4 - 318 T allele and CT60G allele carriers were significantly higher in patients than in controls (p <0.05). Upon stimulation, peripheral blood mononuclear cells (PBMCs) carrying the - 318TT and CT60GG genotypes exhibited significantly lower proliferation, IL-2, and IL-4 levels; fewer cytolytic activities; and higher TGF-β levels compared with PBMCs carrying the - 318 CC/CT or CT60 AA/AG genotypes. We also found that CTLA-4 - 318 T/C and CT60 G/A single nucleotide polymorphisms were associated with the severity of cervical cancer. These results indicate that CTLA-4 - 318 T/C and CT60 G/A can affect cervical cancer susceptibility by altering the immune status of an individual.

Association of cytotoxic T-lymphocyte antigen 4 genetic polymorphism, hepatitis C viral infection and B-cell non-Hodgkin lymphoma: an Egyptian study

Abstract Genetic and environmental factors are involved in the pathogenesis of non-Hodgkin lymphoma (NHL). The present study aimed to investigate the association between cytotoxic T-lymphocyte antigen 4 (CTLA-4) genetic polymorphism, hepatitis C virus (HCV) infection and B-cell NHL risk in Egypt. Genotyping of CTLA-4 single nucleotide polymorphisms (SNPs) was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay for 181 adult patients with B-NHL and 200 controls. Our study revealed that CTLA-4 + 49 A/G polymorphism conferred increased risk of B-NHL (odds ratio [OR] = 1.7, 95% confidence interval [CI] = 1.36-2.565). The prevalence of HCV infection in individuals harboring the mutant genotype + 49 A/G and - 318 C/T SNPs was higher in patients with B-NHL and was associated with increased risk of B-NHL (OR = 2.79, 95% CI = 1.24-6.93 for + 49 A/G and OR = 3.9, 95% CI = 1.01-15.98 for - 318 C/T). In conclusion, some SNPs of CTLA-4 are genetic risk factors for B-NHL. Moreover, this study identified an association of CTLA-4 + 49 A/G and - 318 C/T promoter polymorphisms with HCV infection.

Cytotoxic T-lymphocyte antigen-4 genetic variants and risk of Ewing's sarcoma

Despite the knowledge of many genetic alterations present in Ewing's sarcoma (ES), the complexity of this disease precludes placing its biology into a simple conceptual framework. Cytotoxic T-lymphocyte antigen-4 (CTLA-4) can decrease T-cell activation and attenuate antitumor responses. Polymorphisms in the CTLA-4 gene have been shown to be associated with different diseases. Here, we investigated the association of four CTLA-4 gene polymorphisms, -1661A/G (rs4553808), -318C/T (rs5742909), +49G/A (rs231775), and CT60A/G (rs3087243), with ES in the Chinese population. A total of 308 ES cases and 362 healthy controls were recruited and CTLA-4 polymorphisms were tested by polymerase chain reaction-restriction fragment length polymorphism. Results showed that frequencies of the CTLA-4 gene +49AA genotype, +49A allele, and GTAG haplotype were significantly increased in ES patients compared to healthy controls (odds ratio [OR]=2.42, 95% confidence interval [CI] 1.43-4.09, p<0.001; OR 1.38, 95% CI 1.11-1.73, p=0.005, and OR=1.46, 95% CI 1.06-2.02, p=0.020, respectively). We further compared CTLA-4 polymorphisms in ES patients based on different clinical parameters and data revealed that ES patients with metastasis had higher numbers of the +49AA genotype than those without metastasis (p=0.004). These results indicated that the CTLA-4 polymorphism could be a risk factor for ES and suggested a potential role of CTLA-4 in the metastasis of this malignancy.

Heterozygous genetic variations of FOXP3 in Xp11.23 elevate breast cancer risk in Chinese population via skewed X-chromosome inactivation

FOXP3 (forkhead box P3: also known as IPEX, XPID) is not only a hallmark of immunosuppressive regulatory T cells (Tregs), but also an X-linked breast cancer suppressor gene expressed in tumor cells. A two-stage investigation was conducted in individuals from northern, southern and eastern China. Individuals carrying a FOXP3 rs2294021CT genotype showed about 1.5-fold increased risk of breast cancer compared with TT carriers. In a related biochemical assay, the rs2294021C allele was found to significantly enhance transcription activity, leading to higher mRNA levels of FOXP3 compared with T allele. Moreover, the number of Tregs and its corresponding interleukin-10 (IL-10) secretion were elevated whereas the proliferation of antitumor T cells was decreased in the C-allele carriers. The breast cancer oncogenes Her-2/ErbB2 and Skp2 were also found to be significantly inhibited in C-allele carriers. Moreover, skewed X-chromosome inactivation (SXCI) analysis showed that rs2294021CT carriers with SXCI showed higher risk than the homozygous carriers and CT carriers without SXCI, suggesting a possible interaction between the rs2294021CT genotype and SXCI. Taken together, these findings indicate that the rs2294021CT genotype may increase an individual's susceptibility to breast cancer by breaking the balance between Treg-mediated immune tolerance and FOXP3-controlled tumor-suppressive effect.

IL-21 gene polymorphism is associated with the prognosis of breast cancer in Chinese populations

Interleukin (IL)-21, which is secreted by activated CD4(+) T cells and NKT cells, has been found to be able to influence the humoral and cell-mediated immune responses and have potent antitumor activity in animal models. This study was to investigate the impact of genetic polymorphisms in IL-21 on survival of breast cancer. Four TagSNPs of IL-21 (rs12508721C>T, rs907715G>A, rs13143866G>A, rs2221903A>G) were selected and then genotyped in 891 patients with breast cancer in Eastern and Southern Chinese populations. We then examined the associations between these SNPs and overall survival. Potential function of rs12508721C>T and association between this variation and breast cancer prognosis were further studied. Overall, 121 of the patients had died over the followed-up period of 5 years. The IL-21 rs12508721T allele predicted longer five-year survival (HR = 0.347, 95 % CI = 0.187-0.644, P < 0.0001) in the discovery cohort, the independent validation cohort (HR = 0.429, 95 % CI = 0.244-0.755, P = 0.012), and combined group (HR = 0.447, 95 % CI = 0.301-0.667, P < 0.0001). Furthermore, our luciferase assay revealed that rs12508721T variant allele had a higher transcription activity and the RT-PCR and ELISA assay showed that rs12508721 variant genotypes (CT and TT) carriers have more IL-21 expression than CC carriers (P < 0.05). Our present study established a robust association between the functional polymorphism (rs12508721C>T) in IL-21 and prognosis of breast cancer, indicating that this polymorphism may be a potential biomarker for prognosis of breast cancer.

Functional genetic variations in the IL-23 receptor gene are associated with risk of breast, lung and nasopharyngeal cancer in Chinese populations

Interleukin-23 receptor (IL-23R) is a key element in the T-helper 17 cell-mediated inflammatory process, which plays an important role in the pathogenesis of cancer. In this study, we examined whether genetic polymorphisms in IL-23R are associated with cancer risk in 4936 cancer patients and 5664 control subjects from eastern and southern Chinese populations. We found that the C allele of the rs10889677A>C polymorphism in the 3'-untranslated region of IL-23R was inversely associated with risk of multiple types of cancer, including breast cancer, lung cancer and nasopharyngeal carcinoma. Healthy controls who harbored the rs10889677C allele had significantly decreased cancer risk (odds ratio = 0.74, 95% confidence interval = 0.71-0.78) compared with those who harbored the rs10889677A allele. Biochemical analysis demonstrated that the rs10889677A allele disrupted the binding site for the microRNA miR-let-7f, thereby increasing the transcription of the IL-23R in vitro and in vivo. Furthermore, cancer-free individuals carrying the rs10889677CC homozygous genotype had a lower proportion of regulatory T cells (Tregs) and a higher T-cell proliferation rate upon stimulation with concanavalin A than individuals carrying the rs10889677AA homozygous genotype. Our findings indicate that the IL-23R rs10889677A>C polymorphism may influence T-cell proliferation, resulting in changes in the levels of Tregs in vivo and modifying cancer susceptibility.

Generation of autologous tumor-specific T cells for adoptive transfer based on vaccination, in vitro restimulation and CD3/CD28 dynabead-induced T cell expansion

Adoptive cell transfer (ACT) of in vitro expanded autologous tumor-infiltrating lymphocytes (TIL) has been shown to exert therapeutic efficacy in melanoma patients. We aimed to develop an ACT protocol based on tumor-specific T cells isolated from peripheral blood and in vitro expanded by Dynabeads® ClinExVivo™CD3/CD28. We show here that the addition of an in vitro restimulation step with relevant peptides prior to bead expansion dramatically increased the proportion of tumor-specific T cells in PBMC-cultures. Importantly, peptide-pulsed dendritic cells (DCs) as well as allogeneic tumor lysate-pulsed DCs from the DC vaccine preparation could be used with comparable efficiency to peptides for in vitro restimulation, to increase the tumor-specific T-cell response. Furthermore, we tested the use of different ratios and different types of Dynabeads® CD3/CD28 and CD3/CD28/CD137 T-cell expander, for optimized expansion of tumor-specific T cells. A ratio of 1:3 of Dynabeads® CD3/CD28 T-cell expander to T cells resulted in the maximum number of tumor-specific T cells. The addition of CD137 did not improve functionality or fold expansion. Both T-cell expansion systems could generate tumor-specific T cells that were both cytotoxic and effective cytokine producers upon antigen recognition. Dynabeads®-expanded T-cell cultures shows phenotypical characteristics of memory T cells with potential to migrate and expand in vivo. In addition, they possess longer telomeres compared to TIL cultures. Taken together, we demonstrate that in vitro restimulation of tumor-specific T cells prior to bead expansion is necessary to achieve high numbers of tumor-specific T cells. This is effective and easily applicable in combination with DC vaccination, by use of vaccine-generated DCs, either pulsed with peptide or tumor-lysate.

The inhibitory role of b7-h4 in antitumor immunity: association with cancer progression and survival

B7-H4 is one of the most recently identified members of B7 superfamily of costimulatory molecules serving as an inhibitory modulator of T-cell response. B7-H4 is broadly expressed in human peripheral tissues and inducibly expressed in immune cells. The expression of B7-H4 has been observed in various types of human cancer tissues, and its soluble form has been detected in blood samples from cancer patients. However, its precise physiological role is still elusive, as its receptor has not been identified and the expression levels are not consistent. This paper summarizes the pertinent data on the inhibitory role of B7-H4 in antitumor immunity and its association with cancer progression and survival in human patients. The paper also discusses the clinical significance of investigating B7-H4 as potential markers for cancer diagnosis and prognosis, and as therapeutic targets.

Cytotoxic T-lymphocyte antigen-4 +49G/A polymorphism is associated with increased risk of osteosarcoma

BACKGROUND

Cytotoxic T-lymphocyte antigen-4 (CTLA-4) is a potent immunoregulatory molecule that suppresses anti-tumor response by down-regulating T-cell activation. CTLA-4 gene +49G/A polymorphism (rs231775) has been reported to be associated with various cancers.

OBJECTIVE

The objective of this study is to investigate the association between CTLA-4 gene +49G/A polymorphism and the susceptibility to osteosarcoma in the Chinese population.

METHODS

The CTLA-4 variant +49G/A was detected by polymerase chain reaction-restriction fragment length polymorphism in 205 osteosarcoma cases and 216 age-matched healthy controls. Data were analyzed using the Chi-square test.

RESULTS

Frequencies of the CTLA-4 +49AA genotype and the +49A allele were significantly increased in patients with osteosarcoma compared to healthy controls (OR 2.27, p=0.010, and OR 1.41, p=0.015).

CONCLUSIONS

Our data suggest that the +49G/A polymorphism of CTLA-4 gene is associated with increased susceptibility to osteosarcoma.

Combination therapy of established tumors by antibodies targeting immune activating and suppressing molecules

The blockade of immune suppression against antitumor responses is a particularly attractive strategy when combined with agents that promote tumor-specific CTLs. In this study, we have attempted to further improve the CTL induction and potent antitumor efficacy of a combination mAb-based therapy (termed "trimAb therapy") that comprises tumor cell death-inducing anti-death receptor 5 mAb and immune activating anti-CD40 and anti-CD137 mAbs. Among trimAb-treated tumors, the infiltration of CD4(+) Foxp3(+) cells was greater in progressing tumors compared with stable tumors. Blockade of CTLA-4 (CD152)-mediated signals by an antagonistic mAb substantially increased the tumor rejection rate of trimAb therapy, although the immune responses of draining lymph node cells were not augmented. Interestingly, by comparison, additional treatment with agonistic anti-glucocorticoid-induced TNF receptor mAb, antagonistic anti-programmed death-1 (CD279) mAb, or agonistic anti-OX40 (CD134) mAb significantly augmented immune responses of draining lymph node cells, but did not augment the therapeutic effect of trimAb. CD4 T cell depletion reduced the antitumor effect of anti-CTLA-4 mAb treatment alone, but did not reduce the tumor rejection rate of trimAb in conjunction with anti-CTLA-4 mAb. Thus, the blockade of the CTLA-4-mediated inhibitory signal in tumor infiltrating CTL may be the most effective strategy to augment the effect of immune therapies that generate tumor-specific CTL.

Glucocorticoid-induced tumor necrosis factor receptor stimulation enhances the multifunctionality of adoptively transferred tumor antigen-specific CD8+ T cells with tumor regression

We have reported for the first time the significance of effector T-cell multifunctionality in antitumor immunity, suggesting that the appearance of multifunctional/polyfunctional tumor-specific CD8(+) T cells in vivo is a critical determinant of the success of antitumor immunotherapy, and a strategy to induce multifunctionality in effector cells is required for the successful immunotherapy of hosts with progressing tumor. Glucocorticoid-induced tumor necrosis factor receptor (GITR) stimulation has been shown to enhance antitumor immune response. However, its functional impact on adoptively transferred T cells remains unclear. Here, we analyzed the impact of GITR stimulation in vivo on the functional profiles of adoptively transferred CD8(+) T cells specific for murine fibrosarcoma CMS5. GITR stimulation was found to enhance multifunctionality (interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha production and CD107a mobilization as a degranulation marker) in transferred cells at the single-cell level. These cells exhibited upregulated expression of CD25 in draining lymph nodes and increased infiltration in tumor. Mice that received T-cell therapy with GITR stimulation showed reduced Foxp3(+)CD4(+) T cells among tumor infiltrating lymphocytes and increased in vivo cytotoxic T lymphocytes (CTL) activity even with progressing tumor, resulting in enhanced tumor regression. These data strengthen the idea that effector T-cell multifunctionality is a sensitive immune correlate for successful immunotherapy against malignancy and provide an immunological rationale for effective T-cell therapy combined with GITR stimulation.

Serum vascular endothelial growth factor and fibronectin predict clinical response to high-dose interleukin-2 therapy

PURPOSE

High-dose interleukin-2 (IL-2) induces durable therapeutic responses in a small subset of patients with metastatic melanoma and renal cell carcinoma, but simple pretreatment predictors of response have not been identified.

PATIENTS AND METHODS

To identify predictive biomarkers of clinical response, sera from patients treated with high-dose IL-2 were collected for analysis using a customized, multiplex antibody-targeted protein array platform that surveyed expression of soluble factors associated with tumor immunobiology. Soluble factors associated with clinical responses were analyzed using a multivariate permutation test, and survival outcomes were determined using Kaplan-Meier and log-rank tests.

RESULTS

A training set from 10 patients identified 68 potentially relevant soluble factors that were then tested in an independent validation set of 49 patients. Class comparison revealed a cluster of 11 biomarkers that were associated with therapeutic outcome. Vascular endothelial growth factor (VEGF) and fibronectin were identified as independent predictors of response. In particular, high levels of these proteins were correlated with lack of clinical response and decreased overall survival.

CONCLUSION

Serum VEGF and fibronectin are easily measured pretreatment biomarkers that could serve to exclude patients unlikely to respond to IL-2 therapy.

Therapeutic efficacy of antitumor dendritic cell vaccinations correlates with persistent Th1 responses, high intratumor CD8+ T cell recruitment and low relative regulatory T cell infiltration

Despite the increasing number of immunotherapeutic strategies for the treatment of cancer, most approaches have failed to correlate the induction of an anti-tumor immune response with therapeutic efficacy. We therefore took advantage of a successful vaccination strategy-combining dendritic cells and irradiated GM-CSF secreting tumor cells-to compare the immune response induced against 9L gliosarcoma tumors in cured rats versus those with progressively growing tumors. At the systemic level, the tumor specific cytotoxic responses were quite heterogeneous in uncured vaccinated rats, and were surprisingly often high in animals with rapidly-growing tumors. IFN-gamma secretion by activated splenic T cells was more discriminative as the CD4+ T cell-mediated production was weak in uncured rats whereas high in cured ones. At the tumor level, regressing tumors were strongly infiltrated by CD8+ T cells, which demonstrated lytic capacities as high as their splenic counterparts. In contrast, progressing tumors were weakly infiltrated by T cells showing impaired cytotoxic activities. Proportionately to the T cell infiltrate, the expression of Foxp3 was increased in progressive tumors suggesting inhibition by regulatory T cells. In conclusion, the main difference between cured and uncured vaccinated animals does not depend directly upon the induction of systemic cytotoxic responses. Rather the persistence of higher CD4+ Th1 responses, a high intratumoral recruitment of functional CD8+ T cells, and a low proportion of regulatory T cells correlate with tumor rejection.

Dendritic cells: a critical player in cancer therapy?

Cancer immunotherapy seeks to mobilize a patient's immune system for therapeutic benefit. It can be passive, that is, transfer of immune effector cells (T cells) or proteins (antibodies), or active, that is, vaccination. Early clinical trials testing vaccination with ex vivo generated dendritic cells (DCs) pulsed with tumor antigens provide a proof-of-principle that therapeutic immunity can be elicited. Yet, the clinical benefit measured by regression of established tumors in patients with stage IV cancer has been observed in a fraction of patients only. The next generation of DC vaccines is expected to generate large numbers of high avidity effector CD8 T cells and to overcome regulatory T cells and suppressive environment established by tumors, a major obstacle in metastatic disease. Therapeutic vaccination protocols will combine improved DC vaccines with chemotherapy to exploit immunogenic chemotherapy regimens. We foresee adjuvant vaccination in patients with resected tumors but at high risk of relapse to be based on in vivo targeting of DCs with fusion proteins containing anti-DCs antibodies, antigens from tumor stem/propagating cells, and DC activators.

Functional genetic variations in cytotoxic T-lymphocyte antigen 4 and susceptibility to multiple types of cancer

Antitumor T lymphocytes play a pivotal role in immunosurveillance of malignancy. The CTL antigen 4 (CTLA-4) is a vital negative regulator of T-cell activation and proliferation. This study examined whether genetic polymorphisms in CTLA-4 are associated with cancer susceptibility. A two-stage investigation using haplotype-tagging single nucleotide polymorphism approach and multiple independent case-control analyses was performed to assess the association between CTLA-4 genotypes and cancer risk. Functional relevance of the polymorphisms was examined by biochemical assays. We found that the 49G>A polymorphism in the CTLA-4 leading sequence causing (17)Ala to (17)Thr amino acid substitution is associated with increased susceptibility to multiple cancers, including lung, breast, esophagus, and gastric cardia cancers. Genotyping in 5,832 individuals with cancer and 5,831 control subjects in northern and southern Chinese populations showed that the CTLA-4 49AA genotype had an odds ratio of 1.72 (95% confidence interval, 1.50-2.10; P = 3.4 x 10(-7)) for developing cancer compared with the 49GG genotype. Biochemical analyses showed that CTLA-4-(17)Thr had higher capability to bind B7.1 and stronger inhibitory effect on T-cell activation compared with CTLA-4-(17)Ala. T cells carrying the 49AA genotype had significantly lower activation and proliferation rates compared with T cells carrying the 49GG genotype upon stimulation. These results are consistent with our hypothesis and indicate that genetic polymorphisms influencing T-cell activation modify cancer susceptibility.

Sustained activation and tumor targeting of NKT cells using a CD1d-anti-HER2-scFv fusion protein induce antitumor effects in mice

Invariant NKT (iNKT) cells are potent activators of DCs, NK cells, and T cells, and their antitumor activity has been well demonstrated. A single injection of the high-affinity CD1d ligand alpha-galactosylceramide (alphaGalCer) leads to short-lived iNKT cell activation followed, however, by long-term anergy, limiting its therapeutic use. In contrast, we demonstrated here that when alphaGalCer was loaded on a recombinant soluble CD1d molecule (alphaGalCer/sCD1d), repeated injections led to sustained iNKT and NK cell activation associated with IFN-gamma secretion as well as DC maturation in mice. Most importantly, when alphaGalCer/sCD1d was fused to a HER2-specific scFv antibody fragment, potent inhibition of experimental lung metastasis and established s.c. tumors was obtained when systemic treatment was started 2-7 days after the injection of HER2-expressing B16 melanoma cells. In contrast, administration of free alphaGalCer at this time had no effect. The antitumor activity of the CD1d-anti-HER2 fusion protein was associated with HER2-specific tumor localization and accumulation of iNKT, NK, and T cells at the tumor site. Targeting iNKT cells to the tumor site thus may activate a combined innate and adaptive immune response that may prove to be effective in cancer immunotherapy.

Enhanced efficacy and reduced toxicity of multifactorial adjuvants compared with unitary adjuvants as cancer vaccines

Identification of Toll-like receptors (TLRs) and their ligands, and tumor necrosis factor-tumor necrosis factor receptor (TNF-TNFR) pairs have provided the first logical, hypothesis-based strategies to molecularly concoct adjuvants to elicit potent cell-mediated immunity via activation of innate and adaptive immunity. However, isolated activation of one immune pathway in the absence of others can be toxic, ineffective, and detrimental to long-term, protective immunity. Effective engineered vaccines must include agents that trigger multiple immunologic pathways. Here, we report that combinatorial use of CD40 and TLR agonists as a cancer vaccine, compared with monotherapy, elicits high frequencies of self-reactive CD8(+) T cells, potent tumor-specific CD8(+) memory, CD8(+) T cells that efficiently infiltrate the tumor-burdened target organ; therapeutic efficacy; heightened ratios of CD8(+) T cells to FoxP3(+) cells at the tumor site; and reduced hepatotoxicity. These findings provide intelligent strategies for the formulation of multifactorial vaccines to achieve maximal efficacy in cancer vaccine trials in humans.

Taming cancer by inducing immunity via dendritic cells

Immunotherapy seeks to mobilize a patient's immune system for therapeutic benefit. It can be passive, i.e. transfer of immune effector cells (T cells) or proteins (antibodies), or active, i.e. vaccination. In cancer, passive immunotherapy can lead to some objective clinical responses, thus demonstrating that the immune system can reject tumors. However, passive immunotherapy is not expected to yield long-lived memory T cells that might control tumor outgrowth. Active immunotherapy with dendritic cell (DC)-based vaccines has the potential to induce both tumor-specific effector and memory T cells. Early clinical trials testing vaccination with ex vivo-generated DCs pulsed with tumor antigens provide a proof-of-principle that therapeutic immunity can be elicited. Yet, there is a need to improve their efficacy. The next generation of DC vaccines is expected to generate large numbers of high-avidity effector CD8(+) T cells and to overcome regulatory T cells. Therapeutic vaccination protocols will combine improved ex vivo DC vaccines with therapies that offset the suppressive environment established by tumors.

Ecto-calreticulin in immunogenic chemotherapy

The conventional treatment of cancer relies upon radiotherapy and chemotherapy. Such treatments supposedly mediate their effects via the direct elimination of tumor cells. Nonetheless, there are circumstances in which conventional anti-cancer therapy can induce a modality of cellular demise that elicits innate and cognate immune responses, which in turn mediate part of the anti-tumor effect. Although different chemotherapeutic agents may kill tumor cells through an apparently homogeneous apoptotic pathway, they differ in their capacity to stimulate immunogenic cell death. We discovered that the pre-apoptotic translocation of intracellular calreticulin (endo-CRT) to the plasma membrane surface (ecto-CRT) is critical for the recognition and engulfment of dying tumor cells by dendritic cells. Thus, anthracyclines and gamma-irradiation that induce ecto-CRT cause immunogenic cell death, while other pro-apoptotic agents (such as mitomycin C and etoposide) induce neither ecto-CRT nor immunogenic cell death. Depletion of CRT abolishes the immunogenicity of cell death elicited by anthracyclines, while exogenous supply of CRT or enforcement of CRT exposure by pharmacological agents that favor CRT translocation can enhance the immunogenicity of cell death. For optimal anti-tumor vaccination and immunogenic chemotherapy, the same cells have to expose ecto-CRT and to succumb to apoptosis; if these events affect different cells, no anti-tumor immune response is elicited. These results may have far reaching implications for tumor immunology because (i) ecto-CRT exposure by tumor cells allows for the prediction of therapeutic outcome and because (ii) the re-establishment of ecto-CRT may ameliorate the efficacy of chemotherapy.

The B7 family and cancer therapy: costimulation and coinhibition

The activation and development of an adaptive immune response is initiated by the engagement of a T-cell antigen receptor by an antigenic peptide-MHC complex. The outcome of this engagement is determined by both positive and negative signals, costimulation and coinhibition, generated mainly by the interaction between the B7 family and their receptor CD28 family. The importance of costimulation and coinhibition of T cells in controlling immune responses is exploited by tumors as immune evasion pathways. Absence of the expression of costimulatory B7 molecules renders tumors invisible to the immune system, whereas enhanced expression of inhibitory B7 molecules protects them from effective T cell destruction. Therefore, the manipulation of these pathways is crucial for developing effective tumor immunotherapy. Translation of our basic knowledge of costimulation and coinhibition into early clinical trials has shown considerable promise.

The combination of ionizing radiation and peripheral vaccination produces long-term survival of mice bearing established invasive GL261 gliomas

PURPOSE

High-grade glioma treatment includes ionizing radiation therapy. The high invasiveness of glioma cells precludes their eradication and is responsible for the dismal prognosis. Recently, we reported the down-regulation of MHC class I (MHC-I) products in invading tumor cells in human and mouse GL261 gliomas. Here, we tested the hypothesis that whole-brain radiotherapy (WBRT) up-regulates MHC-I expression on GL261 tumors and enhances the effectiveness of immunotherapy.

EXPERIMENTAL DESIGN

MHC-I molecule expression on GL261 cells was analyzed in vitro and in vivo by flow cytometry and immunohistochemistry, respectively. To test the response of established GL261 gliomas to treatment, mice with measurable (at CT imaging) brain tumors were randomly assigned to four groups receiving (a) no treatment, (b) WBRT in two fractions of 4 Gy, (c) vaccination with irradiated GL261 cells secreting granulocyte-macrophage colony-stimulating factor, or (d) WBRT and vaccination. Endpoints were tumor response and survival.

RESULTS

An ionizing radiation dose of 4 Gy maximally up-regulated MHC-I molecules on GL261 cells in vitro. In vivo, WBRT induced the expression of the beta2-microglobulin light chain subunit of the MHC class I complex on glioma cells invading normal brain and increased CD4+ and CD8+ T cell infiltration. However, the survival advantage obtained with WBRT or vaccination alone was minimal. In contrast, WBRT in combination with vaccination increased long-term survival to 40% to 80%, compared with 0% to 10% in the other groups (P < 0.002). Surviving animals showed antitumor immunity by rejecting challenge tumors.

CONCLUSION

Ionizing radiation can be successfully combined with peripheral vaccination for the treatment of established high-grade gliomas.

Engagement of TLR3, TLR7, and NKG2D regulate IFN-gamma secretion but not NKG2D-mediated cytotoxicity by human NK cells stimulated with suboptimal doses of IL-12

NK cells express different TLRs, such as TLR3, TLR7, and TLR9, but little is known about their role in NK cell stimulation. In this study, we used specific agonists (poly(I:C), loxoribine, and synthetic oligonucleotides containing unmethylated CpG sequences to stimulate human NK cells without or with suboptimal doses of IL-12, IL-15, or IFN-alpha, and investigated the secretion of IFN-gamma, cytotoxicity, and expression of the activating receptor NKG2D. Poly(I:C) and loxoribine, in conjunction with IL-12, but not IL-15, triggered secretion of IFN-gamma. Inhibition of IFN-gamma secretion by chloroquine suggested that internalization of the TLR agonists was necessary. Also, secretion of IFN-gamma was dependent on MEK1/ERK, p38 MAPK, p70(S6) kinase, and NF-kappaB, but not on calcineurin. IFN-alpha induced a similar effect, but promoted lesser IFN-gamma secretion. However, cytotoxicity (51Cr release assays) against MHC class I-chain related A (MICA)- and MICA+ tumor targets remained unchanged, as well as the expression of the NKG2D receptor. Excitingly, IFN-gamma secretion was significantly increased when NK cells were stimulated with poly(I:C) or loxoribine and IL-12, and NKG2D engagement was induced by coculture with MICA+ tumor cells in a PI3K-dependent manner. We conclude that resting NK cells secrete high levels of IFN-gamma in response to agonists of TLR3 or TLR7 and IL-12, and this effect can be further enhanced by costimulation through NKG2D. Hence, integration of the signaling cascades that involve TLR3, TLR7, IL-12, and NKG2D emerges as a critical step to promote IFN-gamma-dependent NK cell-mediated effector functions, which could be a strategy to promote Th1-biased immune responses in pathological situations such as cancer.

Dynamic cross-talk between tumor and immune cells in orchestrating the immunosuppressive network at the tumor microenvironment

Accumulating evidence indicates that a dynamic cross-talk between tumors and the immune system can regulate tumor growth and metastasis. Increased understanding of the biochemical nature of tumor antigens and the molecular mechanisms responsible for innate and adaptive immune cell activation has revolutionized the fields of tumor immunology and immunotherapy. Both the protective effects of the immune system against tumor cells (immunosurveillance) and the evasion of tumor cells from immune attack (tumor-immune escape) have led to the concept of cancer immunoediting, a proposal which infers that a bidirectional interaction between tumor and inflammatory/regulatory cells is ultimately responsible for orchestrating the immunosuppressive network at the tumor site. In this context, a major challenge is the potentiation or redirection of tumor antigen-specific immune responses. The success in reaching this goal is highly dependent on an improved understanding of the interactions and mechanisms operating during the different phases of the cancer immunoediting process. In this review, we discuss the multiple defense and counterattack strategies that tumors have devised in order to evade immune attack and to thwart the effectiveness of several immunotherapeutic approaches.

Immunosuppressive strategies that are mediated by tumor cells

Despite major advances in understanding the mechanisms leading to tumor immunity, a number of obstacles hinder the successful translation of mechanistic insights into effective tumor immunotherapy. Such obstacles include the ability of tumors to foster a tolerant microenvironment and the activation of a plethora of immunosuppressive mechanisms, which may act in concert to counteract effective immune responses. Here we discuss different strategies employed by tumors to thwart immune responses, including tumor-induced impairment of antigen presentation, the activation of negative costimulatory signals, and the elaboration of immunosuppressive factors. In addition, we underscore the influence of regulatory cell populations that may contribute to this immunosuppressive network; these include regulatory T cells, natural killer T cells, and distinct subsets of immature and mature dendritic cells. The current wealth of preclinical information promises a future scenario in which the synchronized blockade of immunosuppressive mechanisms may be effective in combination with other conventional strategies to overcome immunological tolerance and promote tumor regression.

Indoleamine 2,3-dioxygenase and tumor-induced tolerance

Tumors arise from normal cells of the body through genetic mutation. Although such genetic mutation often leads to the expression of abnormal antigens, the immune system fails to respond effectively to these antigens; that is, it is tolerant of these antigens. This acquired state of tolerance must be overcome for cancer immunotherapy to succeed. Indoleamine 2,3-dioxygenase (IDO) is one molecular mechanism that contributes to tumor-induced tolerance. IDO helps create a tolerogenic milieu in the tumor and the tumor-draining lymph nodes, both by direct suppression of T cells and enhancement of local Treg-mediated immunosuppression. It can also function as an antagonist to other activators of antitumor immunity. Therefore, strategies to block IDO might enhance the effectiveness of tumor immunotherapy.

Recent Advances and Current Challenges in Tumor Immunology and Immunotherapy

Despite advances in animal studies, where the cure of the majority of mice with pre-established (albeit early-stage) tumors has become almost standard, human clinical trials have been much less successful. Here we describe some of the most recent advances in the specialist field of tumor immunology and immunotherapy, highlighting salient work to identify key problem areas and potential solutions. We make particular note of recent developments in adoptive therapy; whole-cell, DNA, and peptide vaccines; and antibody therapy. We also describe the revival of interest in regulatory T cells and conclude by detailing the need for clinical trial read-out autonomy and methods to predict which patients will respond to a particular treatment.

Tumor Antigen–Specific T-Cell Expansion Is Greatly Facilitated by In vivo Priming

PURPOSE

Adoptive T-cell therapy is a promising strategy for the treatment of patients with established tumors but is often limited to specific cancers where tumor-infiltrating lymphocytes, the source of T cells for ex vivo culture, can be obtained. In this study, we evaluated the feasibility of expanding HER-2/neu-specific T cells derived from peripheral blood ex vivo following in vivo priming with a HER-2/neu peptide vaccine.

EXPERIMENTAL DESIGN

Peripheral blood mononuclear cells from cytomegalovirus (CMV)-seronegative and CMV-seropositive donors as well as HER-2/neu-positive cancer patients who had or had not been vaccinated with a HER-2/neu peptide-based vaccine was used as a source of T lymphocytes. Antigen-specific T-cell lines were generated by in vitro stimulation with antigen followed by nonspecific expansion on CD3/CD28 beads. The ability to expand antigen-specific T cells was assessed using IFN-gamma and granzyme B enzyme-linked immunosorbent spot. The phenotype of the resultant T-cell lines was evaluated by flow cytometry, including the presence of FOXP3-expressing CD4(+) T cells.

RESULTS

The frequencies of CMV-specific T cells generated from CMV(+) donors were >11-fold higher than the frequencies from CMV(-) donors (P = 0.001), with 22-fold increase of total number of CD3(+) T cells. The frequencies of HER-2/neu-specific T cells generated from the primed patients were >25-fold higher than the frequencies from unvaccinated patients (P = 0.006), with an average of a 19-fold increase of total number of CD3(+) T cells. Using peripheral blood as the source of T cells did not result in concurrent expansion of FOXP3(+)CD4(+) regulatory T cells despite the use of interleukin-2 in in vitro culture. Both CD4(+) and CD8(+) HER-2/neu-specific T cells could be expanded. The extent of ex vivo expansion correlated with the magnitude of immunity achieved during immunization (P = 0.008).

CONCLUSION

Tumor-specific T cells can be efficiently expanded from the peripheral blood ex vivo following in vivo priming with a vaccine. This approach provides an effective method to generate tumor-specific polyclonal T cells for therapeutic use that could be applied to cancer patients with any tumor type.

Breast cancer: should gastrointestinal bacteria be on our radar screen?

Anti-inflammatory drugs and antibiotics alter the risk of breast cancer in women, but roles for bacteria and inflammation in breast malignancies are poorly understood. A recent study in mice suggests that intestinal bacteria can trigger mammary carcinoma. The mechanisms involved in this effect suggest that dysregulated host immune responses to enteric bacteria can influence the development of extraintestinal cancers, highlighting the opportunities for prevention and treatment aimed at promoting intestinal homeostasis.

Liposomal vaccines--targeting the delivery of antigen

Vaccines that can prime the adaptive immune system for a quick and effective response against a pathogen or tumor cells, require the generation of antigen (Ag)-specific memory T and B cells. The unique ability of dendritic cells (DCs) to activate naïve T cells, implies a key role for DCs in this process. The generation of tumor-specific CD8(+) cytotoxic T cells (CTLs) is dependent on both T cell stimulation with Ag (peptide-MHC-complexes) and costimulation. Interestingly, tumor cells that lack expression of T cell costimulatory molecules become highly immunogenic when transfected to express such molecules on their surface. Adoptive immunotherapy with Ag-pulsed DCs also is a strategy showing promise as a treatment for cancer. The use of such cell-based vaccines, however, is cumbersome and expensive to use clinically, and/or may carry risks due to genetic manipulations. Liposomes are particulate vesicular lipid structures that can incorporate Ag, immunomodulatory factors and targeting molecules, and hence can serve as potent vaccines. Similarly, Ag-containing plasma membrane vesicles (PMV) derived from tumor cells can be modified to incorporate a T cell costimulatory molecule to provide both TCR stimulation, and costimulation. PMVs also can be modified to contain IFN-gamma and molecules for targeting DCs, permitting delivery of both Ag and a DC maturation signal for initiating an effective immune response. Our results show that use of such agents as vaccines can induce potent anti-tumor immune responses and immunotherapeutic effects in tumor models, and provide a strategy for the development of effective vaccines and immunotherapies for cancer and infectious diseases.

MUC1-specific immune therapy generates a strong anti-tumor response in a MUC1-tolerant colon cancer model

A MUC1-based vaccine was used in a preclinical model of colon cancer. The trial was conducted in a MUC1-tolerant immune competent host injected with MC38 colon cancer cells expressing MUC1. The vaccine included: MHC class I-restricted MUC1 peptides, MHC class II-restricted pan-helper-peptide, unmethylated CpG oligodeoxynucleotide, and granulocyte macrophage-colony stimulating factor. Immunization was successful in breaking MUC1 self-tolerance, and in eliciting a robust anti-tumor response. The vaccine stimulated IFN-gamma-producing CD4(+) helper and CD8(+) cytotoxic T cells against MUC1 and other undefined MC38 tumor antigens. In the prophylactic setting, immunization caused complete rejection of tumor cells, while in the therapeutic regimen, tumor burden was significantly reduced.

The clinical utility of cytotoxic T lymphocyte antigen 4 abrogation by human antibodies

The recent cloning and identification of a variety of regulatory and counter-regulatory molecules on T cells and antigen presenting cells has led to the development of antibodies and other molecules that either stimulate or abrogate these immune functions. Patients with autoimmune disease, graft rejection and cancer might benefit from the ability to manipulate immune regulatory pathways. The first demonstration of clinical benefit by modulation of immune regulation in cancer involves the use of human antibodies against cytotoxic T lymphocyte antigen 4. Murine preclinical studies suggested that cytotoxic T lymphocyte antigen-4 abrogation would provide clinical benefit after an antitumor vaccination. Early trials of this antibody in patients with melanoma have shown antitumor activity with and without vaccines that is associated with a state of autoimmunity. Surprisingly, the reversal of the state of autoimmunity induced by cytotoxic T lymphocyte antigen 4 antibodies by the use of corticosteroids does not eliminate clinical benefit.

Antibody Targeting to a Class I MHC-Peptide Epitope Promotes Tumor Cell Death

Therapeutic mAbs that target tumor-associated Ags on the surface of malignant cells have proven to be an effective and specific option for the treatment of certain cancers. However, many of these protein markers of carcinogenesis are not expressed on the cells' surface. Instead these tumor-associated Ags are processed into peptides that are presented at the cell surface, in the context of MHC class I molecules, where they become targets for T cells. To tap this vast source of tumor Ags, we generated a murine IgG2a mAb, 3.2G1, endowed with TCR-like binding specificity for peptide-HLA-A*0201 (HLA-A2) complex and designated this class of Ab as TCR mimics (TCRm). The 3.2G1 TCRm recognizes the GVL peptide (GVLPALPQV) from human chorionic gonadotropin beta presented by the peptide-HLA-A*0201 complex. When used in immunofluorescent staining reactions using GVL peptide-loaded T2 cells, the 3.2G1 TCRm specifically stained the cells in a peptide and Ab concentration-dependent manner. Staining intensity correlated with the extent of cell lysis by complement-dependent cytotoxicity (CDC), and a peptide concentration-dependent threshold level existed for the CDC reaction. Staining of human tumor lines demonstrated that 3.2G1 TCRm was able to recognize endogenously processed peptide and that the breast cancer cell line MDA-MB-231 highly expressed the target epitope. The 3.2G1 TCRm-mediated CDC and Ab-dependent cellular cytotoxicity of a human breast carcinoma line in vitro and inhibited in vivo tumor implantation and growth in nude mice. These results provide validation for the development of novel TCRm therapeutic reagents that specifically target and kill tumors via recognition and binding to MHC-peptide epitopes.

Viral Vaccines for Cancer Immunotherapy

The understanding that tumor cells can be recognized and eliminated by the immune system has led to intense interest in the development of cancer vaccines. Viruses are naturally occurring agents that cause human disease but have the potential to prevent disease when attenuated forms or subunits are used as vaccines before exposure. A large number of viruses have been engineered as attenuated vaccines for the expression of tumor antigens, immunomodulatory molecules, and as vehicles for direct destruction of tumor cells or expression of highly specific gene products. This article focuses on the major viruses that are under development as cancer vaccines, including the poxviruses, adenoviruses, adeno-associated viruses, herpesviruses, retroviruses, and lentiviruses. The biology supporting these viruses as vaccines is reviewed and clinical progress is reported.